Protozoans hunt,
digest and store food. Most are heterotrophs. They feed on other
animals to obtain the nutrients they need to live.

Movement

Protozoans move
by the use of cilia, flagella, pseudopods or some have no movement (Sporozoa).

Defense

When too much
water collects in the cell, the vacuole move to the outer surface of the
cell and squeezes out the water. This stops the cell from swelling up and
bursting.

Reproduction

Asexual reproduction
of protozoans occurs when the cell divides in half by binary fission.
Some which are parasites multiply within the host. Some protozoans
reproduce sexually as well. This can happen when two protozoans carrying
half of their regular genetic material fuse together and form a new cell.
Others exchange genetic material during mating.

Respiration

Respiration
takes place when oxygen diffuses into the cell, where the food molecules
become oxidized. The energy produced and the organic molecules are
used for maintenance and building of the cell. Waste products ,carbon
dioxide and water diffuse out of the cell.

Excretion

Waste materials
in protozoans are removed from the cell by diffusion through the cell.
They are transported out of the cell by food vacuoles that come in
contact with the surface. This is known as exocytosis.

Rhizopods

General Characteristics

motile (pseudopod)
eukaryote
heterotroph

Taxonomic Breakdown

Kingdom

Protista

Phylum

Sarcodina

Nutrition

They engulf
their food with their pseudopods where it then forms a food vacuole. This
is where the food is broken down and spread throughout the rhizopod. This
process is called phagocytosis.

Movement

They move with
the use of their pseudopods.

Reproduction

Amoebas, under
favorable conditions, reproduce by binary fission (This means dividing
in two), producing two daughter amoebas. The nucleus divides by mitosis.
If ameobas are divided artificially the nucleus does not divide.
Only the half of the amoeba containing the nucleus survives while the other
half dies. If conditions are unfavorable the amoeba will secrete
a protective covering and wait until conditions are favorable to divide.

Excretion

Materials that
are useless to the amoeba are held in the food vacuole until the vacuole
comes in contact with the membrane of the body surface. This is where the
waste is expelled from the body

Respiration

Respiration
takes place by diffusion of gases through the cell membrane

Defense

The Arcella,
known as a domed Amoeba, builds a transparent dome from whatever building
materials it can find in the pond, usually sand. It then encloses itself
in the dome for protection.

Economic Importance

The skeletons
of Foramininfera make up much of the limestone and chalk on the
Earth.

It swims rapidly
by coordinated wavelike beats of its many cilia. A paramecium normally
moves forward in a corkscrew fashion but is capable of reversing direction
when it encounters undesirable conditions.

Reproduction

The larger nucleus
is thought to regulate cell functions, while the smaller nucleus is involved
in reproduction. Ciliates usually reproduce asexually by binary fission.
Sometimes they reproduce sexually. This takes place when two individual
ciliates join together at the oral grooves and exchange portions of the
micronuclei. After this stage each individual divides.

Nutrition

At one side
of the ciliates body there is a mouth like opening called the oral groove.
The food is swept into the oral groove by the cilia. Food consists
of other protozoans, bacteria and algae.

Excretion

Undigested food
is discarded through the anal pore (which is some distance behind the oral
groove). Metabolic wastes diffuse out directly at the body surface.

Respiration

Respiration
of Ciliates can be anaerobic (occurring without oxygen) or aerobic (requiring
oxygen). Anaerobic protozoa must live without oxygen and will die
if exposed to it. Respiration rate varies directly with temperature
and also depends on the kind of molecules broken down for energy.
It also varies with species.

Defense

In many ciliates
there is a layer of many tiny carrot shaped bodies, called Trichocysts,
underneath the pellicle. When discharged each Trichocysts forms a
long sticky thread. Usually they are discharged as a means of defense
but are sometimes used as an anchor.

Sporozoans have
no physical form of movement. However, they can be moved by the currents
of the blood or other fliuds of their hosts.

Reproduction

They reproduce
sexually in one host and then asexually in a second host.

Nutrition

They are
parasites. Sporozoans have special organelles that allow it to invade
a host cell.

Defense

The Plasmodium
vivax(Sporozoan) tucks inside the red blood cells, where the parasites
are protected from attack by the antibodies of the host. Even when they
leave to invade fresh cells, they evade immune destruction by constantly
changing their antigens [any of several subsatnces that cause the development
of antibodies].